Epidemiology

NLPHL accounts for
approximately 5% of all Hodgkin lymphomas. There is a unimodal age
distribution; patients are predominantly male and 30-50 years old.

Clinical features

Usually involves
cervical, axillary or inguinal nodes, most cases presenting as stage
I or II disease. Some cases are preceded by biopsies progressive
transformation of germinal centres, but most cases of PTGC do not
progress to NLPHL. Thymic involvement is rare2.

Histopathology

The nodal
architecture is replaced by a nodular or nodular and diffuse
infiltrate composed of small lymphocytes and scattered L&H cells.
L&H cells have a single large nucleus, often folded or
multilobated to form a "popcorn" cell. Nucleoli are usually
small, multiple, peripheral and basophilic. Cytoplasm is scanty.
Histiocytes and plasma cells may be seen but neutrophils and
eosinophils are absent.

Immunohistochemistry

The L&H cells are rosetted by
CD3+/CD57+/bcl-6+ T cells. These help to distinguish from PTGC,
LR-CHL and (most) THRLBCL,
which lack these rosetting T cells2.

Oct-2 and BOB.1
are co-activators of immunoglobulin synthesis and may prove useful in
differentiated NLPHL (positive for both) from classical HL (never
positive for both). The transcription factor PU.1
is also regularly expressed in NLPHL but not in CHL or THRLBCL2.

CD20 and CD21 are useful in
demonstrating nodularity when it is subtle.

Differential diagnosis

PTGC; CD20 and EMA
may help to highlight sparse neoplastic cells1.

One nodule showing
the features of NLPHL is sufficient to establish the diagnosis. It is
uncertain whether purely diffuse lymphocyte predominant Hodgkin
lymphoma exists; most cases should be reclassified as;

lymphocyte rich
classical Hodgkin lymphoma. There may be minimal sclerosis or some
classical RS or lacunar cells; immunophenotype is then crucial2.

Prognosis

NLPHL is usually very
indolent, with prolonged disease-free intervals, albeit with frequent
late relapses. Stage I & II; 10 year survival >80%. Advanced
stage has a poor prognosis. 3-5% of case progress to large B cell
lymphoma, although if localised this retains a good prognosis.

References

World Health Organization Classification of Tumours, Tumours of the
haematopoietic and lymphoid tissues, IARC Press 2001.